Essential hypertension is a serious health problem accounting for approximately 90% of the 24 million cases of high blood pressure in the United States (see Marx, J. L., Science 194 821-5, 1976). Excessive salt (NaCl) intake is believed to be an important factor in its development. The average intake of salt by adults in the U.S. is 10-12 g/day, only one third of which comes from the natural foodstuffs making up the diet with the remaining two thirds provided by sodium chloride added by the consumer or by the food manufacturer to improve palatability. Thus, an effective means for reducing sodium intake in the diet while maintaining the overall palatability of foodstuffs would have great value.
Numerous attempts have been made to develop sodium-free salt substitutes based on potassium chloride but without notable success owing to the pronounced bitterness which potassium chloride displays in addition to its salty character. Various stratagems have been used to mask the bitter flavor and provide acceptable palatability. Thus, U.S. Pat. No. 4,243,691 discloses a sodium free salt substitute which comprises a 5'-nucleotide component, an amino acid mixture, a sugar component, potassium phosphate, and potassium chloride. The amino acid mixture, which may include aspartic acid among its components, comprises a substantial fraction (10-40%) of the composition. U.S. Pat. No. 2,829,056 discloses a sodium free dietary seasoning composition based on a mixture of various basic and acidic amino acid salts plus potassium chloride.
U.S. Pat. No. 4,340,614 reveals a stringently sodium-restricted dietetic salt substitute consisting of potassium chloride mixed with the potassium salts of adipic, tartaric, and glutamic acid plus a 5'-nucleotide.
Other attempts to provide sodium-free salt substitutes have relied on the use of mixtures of the salt forms of various amino acids and peptides. The monohydrochloride salts of the basic dipeptides ornithyltaurine and ornithyl-beta-alanine were reported to have a salty taste (see Tada, M. et al., J. Agric. Biol. Chem. 32:992, 1984). French Patent No. 2,547,992 discloses a salty-flavored composition comprising glutamic acid and aspartic acid either in acid form or as non-sodium salts. U.S. Pat. No. 2,500,919 reveals a sodium-free seasoning composition capable of yielding monopotassium glutamate in the presence of water as a meat flavoring agent.
A chloride-free product with a saline taste is revealed in U.S. Pat. No. 1,874,055 comprising the alkali metal salt of formic, acetic or lactic acid with glutamic acid or a protein hydrolysate capable of yielding mixtures of different amino acids. In general, attempts to provide sodium-free or low sodium salt substitutes has met with only partial success because such compositions either have low saltiness value when compared to sodium chloride, have off-flavors associated therewith or otherwise do not provide a seasoning quality equal to that of sodium chloride. Moreover, some salt substitutes that have been proposed are unavailable or are extremely expensive as compared to ordinary table salt as for example, ornithyl-beta-alanine, and ornithyltaurine, and therefore do not represent a practical means for a meaningful reduction of sodium in the diet.
Tamura et al. (see Agric. Biol. Chem., 53(6):1625-33, 1989) have shown that the saltiness of sodium chloride in aqueous solution can be modified by the addition of the hydrochloride salts of certain amino compounds (amino acids and amino acid esters). Both enhancement of salty flavor and diminishment of salty flavor was observed when the amino compound was present at concentrations ranging from 0.0075 to 0.045 molar. In many cases, a sour, bitter, umami, or other undesirable off-flavor was also introduced owing to the high concentration of amino compound tested. The pronounced tendency of acidic amino acids, for example, glutamic acid, to contribute undesirable umami flavor was pointed out. It is known that L-aspartic acid alone in water solutions imparts a sour taste while L-arginine alone imparts a bitter taste.